1. Field of the Invention
The present invention relates to a flexible manufacturing system and control method therefor, more particularly, to a flexible manufacturing system and control method therefor in which each of plural workpiece transfer units holding a workpiece to be machined thereon is input from one end of a machining line and output from the other end thereof in turn, and plural machining operations are performed to the workpiece by selectively coming into contact with plural cutting tools aligned along a longitudinal direction of the machining line.
2. Description of the Related Art
In a mass-production system for manufacturing a workpiece such an automobile part, there is conventionally adopted a transfer machine in which plural machine tools in which sole machining function is carried out are aligned along a machining line. However, there is recently adopted such a flexible transfer line (referred to as "FTL" hereinafter) of a type in which a plurality of machine tool having an automatic tool changer (referred to as "ATC" hereinafter) are disposed in the machining line instead of the machine tool with the sole machining function, in order to satisfy the need for flexibility so that different parts are machined in the same line.
In this FTL, it is so configured that the plural machine tools with the ATC are aligned along a direction for transferring a workpiece, and that the workpiece is transferred into each of these machine tools by a workpiece transfer device to perform a machining operation on the workpiece in turn. In such a FTL, there are independently provided the machine tools and the workpiece transfer device for transferring the workpiece between the machine tools. Further, in each of the machine tools, there is provided a workpiece fixing device for loading the workpiece or a pallet to which the workpiece is secured from each of the machine tools to the workpiece transfer device. To the contrary, the workpiece transfer devices are provided in generally the same number as the plural machine tools for transferring the workpiece from one machine tool to an adjacent machine tool.
Furthermore, the aforementioned machine tools with the ATC are so constructed that the variety of the machining operations are automatically continuously performed to the workpiece supported on a worktable by different cutting tools, or grinding tools each of which is selectively attached to a tool spindle. In this case, the ATC is used for releasing the used tool from the tool spindle and for attaching the other tool thereto, at the same time when the machining operation is completed by one tool. Moreover, a tool clamp mechanism is formed in the tool spindle for fixing the tool brought by the ATC to the tool spindle and for releasing the fixed tool therefrom.